Copolymers of vinyl esters of branched acids

ABSTRACT

Copolymers of (a) a vinyl ester of an alpha-branched, saturated, aliphatic monocarboxylic acid of five-20 carbon atoms, (b) an alpha,beta-ethylenically unsaturated carboxylic acid of three to five carbon atoms, (c) a monovinylaromatic compound of eight to nine carbon atoms, (d) a 2-hydroxyalkylester or an amide of an alpha,beta-ethylenically unsaturated carboxylic acid and, optionally, (e) a C1-C4 alkyl ester of acrylic or methacrylic acid and their preparation are described. These special copolymers are especially suitable in water-thinnable compositions, particularly in electrodepositable compositions to produce pore-free coatings or films.

United States Patent Van Westrenen et al.

[ 51 June 13, 1972 COPOLYMERS OF VINYL ESTERS OF BRANCHED ACIDS WilliamJ. Van Westrenen; Pieter De Carpentier, both of Delft; Willem H. M. Newwenhuis, Amsterdam, all of Netherlands Assignee: Shell Oil Company, NewYork, NY.

Filed: June 30, 1970 Appl. No.2 51,326

Inventors:

Foreign Application Priority Data July 3, 1969 Great Britain ..33,543/69US. Cl ..260/78.5 R, 260/29.4 UA, 260/39 R, 260/78.5 T, 260/80.73,260/80.75, 260/844,

260/901, 117/93.4 R, 117/132 BF Int. Cl. ..C08f 15/40 Field of Search..260/80.75, 80.73, 78.5 E, 78.5 R

References Cited UNITED STATES PATENTS 11/1966 Oosterhof et a1. ..260/233,294,727 12/1966 Grommers et al. ..260/29,6 3,455,887 7/1969 Levine..260/78.5

FOREIGN PATENTS OR APPLICATIONS 1,087,623 10/1967 England ..260/85lPrimary Examiner-Joseph L. Schofer Assistant ExaminerStanford M. LevinAttorney-Norris E. Faringer and Martin S. Baer [57] ABSTRACT l 1 Claims,No Drawings COPOLYMERS OF VINYL ESTERS OF BRANCHED ACIDS BACKGROUND OFTHE INVENTION The use of water-thinnable paint binders and paints is nowwell established. One of the advantages is that they offer thepossibility for electrodeposition from aqueous solution onto metals toform a pore-free coating in thin layers, even at places difficult toreach with spray gun or brush. In order to be suitable as a component inwater-thinnable binders, the copolymer must preferably contain carboxylgroups.

SUMMARY OF THE INVENTION The invention relates to special copolymers ofvinyl esters which can be used as binder components in thermosettingcoating compositions, such as in solvent-home stoving lacquers, and inparticular in water-thinnable compositions.

Accordingly, the invention provides a special copolymer which isobtained by copolymerizing in one or more stages a mixture ofethylenically unsaturated compounds consisting of:

a. 20-80 percent by weight of a vinyl ester of saturated aliphaticmonocarboxylic acids having from five-20 carbon atoms per molecule andin which carboxylic acids the carboxyl group is attached direct to atertiary or quaternary carbon atom, i.e., alpha-branched,

b. 2-20 percent by weight of an alpha, beta-ethylenically unsaturatedcarboxylic acid having three to five carbon atoms per molecule,

c. 5-40 percent by weight of a monovinylaromatic compound, having eightto nine carbon atoms per molecule,

d. 5-35 percent by weight of a Z-hydroxyalkylester or an amide of analpha, beta-ethylenically unsaturated carboxylic acid, and, optionally,

e. 0-25 percent by weight of a C to C alkylester of acrylic ormethacrylic acid.

DESCRIPTION OF THE PREFERRED EMBODIMENT For convenience in thisspecification the term present copolymer shall mean the copolymerobtained by copolymerizing components (a), (b), (c), (d) and,optionally, (e). The present copolymers have an average molecular weightof more than 1,000 and the term includes copolymers with randomarrangement of monomer units as well as block copolymers and graftcopolymers, and mixed copolymers.

The main structural units in the present copolymers are:

wherein R is hydrogen or an alkyl group, and R and R are alkyl groups ortogether with the central carbon atom form a eycloalkyl group.

(b) H R wherein each R separately is hydrogen, methyl, or a carboxylgroup.

wherein R is hydrogen or methyl.

wherein each R separately is hydrogen, methyl or ethyl, and each Rseparately 1s hydrogen, methyl, carboxyl or 2-hydroxyalkyl, and,optionally,

(e) n lit wherein R is hydrogen or methyl, and R is a C to C Aqueouscoating compositions containing the present copolymers have goodhydrolytic stability, and yield, when applied by electrodeposition andstoved, films which have good gloss, appearance, flexibility andexcellent chemical resistance.

The binder is usually prepared by neutralizing the copolymer completelyor partially with an alkaline material, such as a nitrogen base.

For convenience the saturated aliphatic monocarboxylic acids in whichthe carboxylic group is attached direct to a tertiary or quaternarycarbon will hereinafter be referred to as branched monocarboxylic acids"or as alpha-branched monocarboxylic acids and the vinyl esters thereofas vinyl esters of branched monocarboxylic acids. Aliphatic" as usedherein includes acyclic aliphatic as well as cycloaliphatic.

For the preparation of the present copolymers, component (a) ispreferably a vinyl ester of alpha-branched monocarboxylic acids havingfrom nine-11, or more specifically 10, carbon atoms per molecule.

The branched monocarboxylic acids can very suitably be obtained byreacting formic acid or carbon monoxide and water with olefins under theinfluence of liquid acid catalysts, such as sulphuric acid, phosphoricacid or complexes of phosphoric acid, borontrifuoride and water. Asolefins in such processes, mixtures of olefins obtained by crackingparaffinic hydrocarbons, for example mineral oil fractions, may be used.These mixtures may contain branched as well as straight chain acyclicolefins and also cyclo-aliphatic olefins. When such mixtures are reactedwith formic acid or with carbon monoxide and water, a mixture ofsaturated acyclic and cycloaliphatic monocarboxylic acids is obtained inwhich the carboxyl group is predominantly attached to a quaternarycarbon atom. Other olefinic starting materials are, for example,isobutylene, propylene trimer, and diisobutylene.

The preparation of suitable alpha-branched, saturated, monocarboxylicacids and their respective vinyl esters is well known. See, for example,U.S. Pat. Nos. 3,287,300 and 3,294,727.

55 The alpha, beta-ethylenically unsaturated carboxylic acids used ascomponent (b) are preferably monocarboxylic acids, and more preferablyacrylic acid or methacrylic acid, but dior polyvalent carboxylic acidsare also included. Examples of dior polyvalent alpha, beta-ethylenicallyunsaturated carbox- 60 ylic acids are maleic acid and fumaric acid andalso dior 5 ic or methacrylic acid, and is preferably methylmethacrylate.

The amount of component (a) is preferably 40-70 percent of the totalweight of monomers.

Preferred amounts of components (b) and (c) are each -25 percent byweight.

Very suitable copolymers for use in water-thinnable binders are obtainedby copolymerizing 40-60 percent by weight of component (a), 4-10 percentby weight of component (b), -30 percent by weight of component (c), 5-20percent by weight of component (d) and 10-25 percent by weight ofcomponent (e).

Other preferred copolymers are obtained by copolymerizing 45-65 percentby weight of component (a), 4-10 percent by weight of component (b),5-30 percent by weight of component (c), and 10-30 percent by weight ofcomponent (d).

The present copolymers can be produced by methods generally known in theart. The polymerization may be performed either without any diluent orin solution, suspension or emulsion.

Preferably, the polymerization is carried out in a solvent in which themonomers are soluble. Suitable solvents are, among others, butanol,isopropanol, monomethyl ether of ethylene glycol, butyl acetate, ethylacetate, benzyl alcohol, cyclohexanon, or isophorone, and thehydrocarbons cyclohexane and xylene. A very suitable solvent for thepolymerization proved to be a 1:2 weight ratio blend of butyl OXITOL andbenzyl a1- cohol, as it noticeably improves flow of coatings on stovingand gloss of the stoved film. For the polymerization, a peroxidecatalyst is generally utilized. Suitable catalysts for this purpose are,among others, di-tertiary butyl peroxide and benzoyl peroxide. Theamount of catalyst that may be utilized may be varied considerably;however, in most cases, it is desirable to use a quantity of catalystthat is from 0.1 to 5.0 percent by weight of the amount of monomer to bepolymerized.

The reaction temperature chosen depends on the catalyst selected and isgenerally between 50 and 150 C. In many cases a reaction temperature ischosen at which the reaction mixture just boils.

For preparing the present copolymers, a process is preferred in which areactor is charged with the total amount of component (a) and with from5 to percent by weight of the other ethylenically unsaturated monomers,whereafter, under polymerization conditions, the remainder of components(b), (c), (d) and, optionally, (e) is added gradually in one or morestages. For preparing five component copolymers the remainder ofthecomponents (b), (c), (d), and (e) may be added gradually in one stage,for example, if the catalyst is benzoyl peroxide at a polymerizationtemperature of from 75 to 130 C, the remainder may be added in onemixture at a constant rate in 10-15 hours. For preparing four componentcopolymers from components (a), (b), (c), and (d), preference is givento a process in which the remainder of components (b), (c), and (d) isadded in two stages, for example a first stage in which 70-90 percent byweight of components (b) and (d) plus the total of the remainder ofcomponent (c) is added gradually, and a second stage in which theremaining amount of components (b) and (d) is added gradually. Anotherpreferred process comprises charging the reactor with the total amountof components (a) and (c) and with from 0-15 wt.-% of the othermonomers, and then adding gradually under polymerization conditions theremainder of components (b), (d), and, optionally, (e) in one or morestages.

Staged additions as hereinbefore described are believed to promotecopolymerization and to reduce homopolymerization of individualcomponents. Monomer components (a) and (c) hardly, if at all,copolymerize because the polymerization rates are widely different;however, if components (b), (d), and, optionally, (e) are present,virtually complete copolymerization can be directed by proper selectionof polymerization technique, such as staging as hereinbefore described.

The present copolymers can be used in therrnosetting paint and lacquerformulations, in combination with formaldehyde condensation productssuch as urea-formaldhyde resins and melamine-formaldehyde resins.Dissolved or dispersed in volatile organic liquids such formulations canbe applied by spray, brush, or roller, or by dipping.

Copolymers according to the invention which contain in the molecule theequivalent of 4-10 percent by weight of component (b) can be madewater-soluble for use in binders by neutralizing wholly or partly withan alkaline material, such as a nitrogen base, e.g., ammonium hydroxideor triethylamine, and further dilution with water. Such aqueoussolutions can be mixed, if desired, with formaldehyde-condensationproducts, such as the low-reactive butylated formaldehyde-melamine resinClBAMIN M 96, for use in electrodeposition paints. The film propertiesof electrodeposition finishes formulated from binders on base of thepresent copolymers are excellent.

The superior performance of the present copolymers in thermosettingsurface coating compositions is attributed to the proper choice ofmonomer components and their weight ratios, in particular to the use ofvinyl aromatic compounds [component(c)] in conjunction with the othertypes of components. For example, it was found that copolymers asdescribed in Example 1 but without styrene were inhomogeneous, and thatpaint films based on them were heterogeneous and locally sticky.

Further, there is improvement in performance over the copolymers ofBritish Pat. No. 1,087,623, which have been obtained by copolymerizing amixture consisting of a VER- SATlC acid 911 vinyl ester which is a vinylester of alphabranched saturated monocarboxylic acids as hereinbeforedefined, an alpha, beta-ethylenically unsaturated carboxylic acid,methyl methacrylate, a C C alkyl acrylate, and a hydroxyalkyl ester ofan alpha, beta-ethylenically unsaturated carboxylic acid, all as moreparticularly described therein, also with respect to the weight ratiosof the monomer components. It has been found that in comparativecompositions, optimalized both with regard to hardness and flexibilityof stoved coatings, the copolymers of the present invention offeradvantages, in particular in electrodeposition paints, with regard tochemical resistance and solvent resistance, as demonstrated by acomparative example below.

The invention is illustrated by the following examples. Parts andpercentages therein are by weight, unless otherwise indicated. Example11 is a comparative example.

EXAMPLE I The present copolymer (to be referred to hereinafter ascopolymer A) was prepared from the following monomer composition:

Type of Monomer Parts by Weight Mixture of vinyl esters of saturatedaliphatic monocarboxylic acids having 9-1 1 C-atoms and branched at the50.0 alpha-C-atom (VEOVA 91 1 Acrylic acid 6.6 Styrene 16.02-hydroxyethyl methacrylate 10.3 Methyl methacrylate l 7. 1

A glass reactor of 1 liter, fitted with stirrer, thermometer, condenser,nitrogen inlet tube and connected via glass tubes to a metering pump,was charged with 200 g of VEOVA 91 1 to which 1 g of di-tertiary butylperoxide was added, and 37.4 g of a comonomer mixture which had thefollowing composition:

Acrylic acid 26.4 g Z-hydroxyethyl methacrylate 41.2 g MethylMethacrylate 68.4 g Styrene 64.0 g Solvent 170.0 g Benzoyl peroxide 4.0g

The solvent was a 1:2 weight ratio blend of ethylene glycol butyl etherand benzyl alcohol.

The reactor charge was heated to 80 C. while continuously stirring thereactor charge and leading nitrogen over the reactor content at a rateof 0.36 l/min. At 80 C. the remaining comonomer mixture (336.6 g) waspumped into the reactor at a constant rate in 12 hours. The temperaturewas increased from 80 C. to 115 C. within half an hour. For controllingexothermic reaction, cooling means are applied.

After the addition of all comonomers 1.5 g of benzoyl peroxide (50 wt.-%paste in phthalate plasticizer) was added and the heating was continuedfor 2 hours. This procedure was repeated three times.

A polymer solution was obtained of which the solids content was 67 wt.-%and the acid value 37.8 mg KOH/g solution. An aqueous solution ofpolymer and melamine formaldehyde resin (the binder solution) wasprepared by blending consecutively:

191.5 g polymer solution prepared as above (67% solids) 42.8 g melamineformaldehyde resin (CIBAMlN M 95; 75 wt.-% solids) 7.8 g triethyl amine399.5 g demineralized water.

The solids content of this binder solution was 25 percent by weight; thepolymer/melamine formaldehyde resin ratio was 80/20 wt. in the same waya binder solution in which the polymer/melamine-formaldehyde resin ratiowas 87/ l 3 was prepared.

A pigment dispersion was then prepared by ball milling:

55 g rutile titanium dioxide 55 g binder solution for 17 hours and thenadding:

100 g of the binder solution and further ball milling for another 2hours. A paint was then prepared by mixing consecutively:

189 g ball mill compound 460.5 g binder solution 850.5 g demineralizedwater. The paint had the following data:

Specific resistance at 23 C. 1,219 .Qcm Pigment/binder ratio 0.33 (wt.)

Total binder solids content percent This paint was deposited ontophosphated steel panels in an electrodeposition bath under the followingconditions:

area coated per panel 230 cm temperature of paint 22 C electrodeseparation 10 cm (anode panel to be coated, cathode stainless steelpanel) Deposition voltage Deposition time Deposition final amperage 100V constant 2 minutes 0.1 A

The properties of the paints are given in Table I.

days adhesion good days adhesion good EXAMPLE ll (Comparative Example)For comparison, a copolymer (to be referred to hereinafter as copolymerB") was prepared according to British Pat. No. 1,087,623 from monomersin the following weight ratios:

Type of Monomer Parts by Weight VEOVA 91 1 26.5 Acrylic acid 6.0 Butylacrylate 25.0 Z-hydroxy ethyl methacrylate 10.0 Methyl methacrylate 32.5

The polymerization was carried out as described in said British Pat.1,087,623, with lauryl mercaptan and di-tert.- butyl peroxide asinitiator and butyl OXITOL as the solvent. The copolymer was neutralizedwith triethyl amine, and compounded into a paint substantially asdescribed in Example I for copolymer A. The properties of the resultingpaint are tabulated in Table II.

TABLE II Film Properties of White Electrodeposition Finishes (CopolymerB) Polymer Melamine formaldehyde resin Polymer/melamine formaldehydeCopolymer B CIBAMIN M 96 resin ratio in bath /20 Pigment rutile titaniumdioxide Pigment/Binder ratio 0 33 Deposition conditions 2 minutes 100 VFilm thickness p.)

Stoving schedule 30 minutes, C Gloss under 45 61 Appearance slightuneven Buchholz hardness 83 Minutes to total softening in Acetone /4Methyl isobutyl ketone -l Xylene At-1 Resistance to 5% NaOl-l, 23 Cafter 5 days total loss of adhesion after 5 days total loss of adhesion5% HAc, 23 C Comparing the film properties of the whiteelectrodeposition finishes based on the copolymers of Example I withthose based on the copolymers of Example 11 prepared according toBritish Pat. No. 1,087,623, it will be apparent that the former havebetter performance, in particular with respect to chemical resistance,solvent resistance and hardness.

EXAMPLE n Some tylgical data of this paint are: 8 8 The copolymer wasprepared from the following monomer :P C 9 cm co p igmen in er ratio(wt) 0.3

This paint was deposited onto cold-rolled steel panels in an M P rts b Wht Type a y as electrodeposition bath under the following conditions:

Mixture of vinyl esters of saturated 57.0 area coated per pane] 150aliphatic monocarboxylic acids temperature of paint 22 C having 9-1 1C-atoms and branched 0 electrode separation cm at the alpha-C-atom(VEOVA 1 l) deposition voltage 250 V constant Methacrylic aciddeposition time 2 minutes Styrene 13.3 deposition final amperage 0.07 AZ-hydroxyethyl methacrylate 22.8

The coated panels were stoved at 175 C. during 30 1 7 minutes; thestoved coatin had the followin r0 ert'es: A glass reactor of 1 liter,fitted with stirrer, thermometer, 85 SP p l condenser, nitrogen inlettube and connected via glass tubes Film thickness 24 to a metenng pump,was charged with the following mixture: Gloss under 74 Buchholz hardness91 VEOVA 91 l 1 9,7 8 Minutes to total softening in: Mehacrylic acid L48 Methyl tsobutylketone 15 Xylene 15 Styrene 8 Resistance to2-hydroxyethyl methyl methacrylate 4.8 g Methyl OXlTOL (Z-methoxyethanol) 30.0 g 5% NaoH' 23 C sft i ll v eg gfi d Tetrahydmfurane g 5%acetic acid, 23" C after 7 days adhesion still very good The reactorcharge was heated to 80 C. w1th continuous w claim asourinvendon;stirring and leading in nitrogen at a rate of 0.36 l/min. 1 A randomcopolymer comprising;

The following mum/"e was P p and P p the a. 20-80 percent by weight ofmonomer units derived from reactor at a constant rate over 18 hours: avinyl ester of alpha-branched, saturated, aliphatic monocarboxylic acidhaving five-20 carbon atoms per methacl'yhc 1 8 molecule, said unitshaving the structural formula: Styrene 25.1 g Z-hydroxyethylmethacrylate 38.4 g H H Methyl OXITOL 37.5 g Tetrahydrofurane 7.5 g -CCBenzoyl peroxide 2.4 g 1 3S Fifteen minutes after begin of this additionthe temperature (13:0 was raised from 80 C. to 110 C. in 20 minutes.Throughout the further reaction time the temperature was maintained at l0 R2 1 10 C. A further mixture consisting of 40 wherein R1 is y g or analkyl p: and R2 and 3 are methacrylic acid Z-hydroxyethyl methacrylatemethyl OXITOL tetrahydrofurane benzoyl peroxide alkyl groups or togetherwith the central carbon atom form a cycloalky] group,

b. 2-20 percent by weight of monomer units derived from an alpha,beta-ethylenically unsaturated carboxylic acid,

said units having the structural formula: was added at a constant rateover 2 hours.

After addition of all comonomers 1.5 g of benzoyl peroxide H R wasadded, and the heating was continued for 4 hours. l The polymer solutionobtained had a solids content of 69 wt.-% and an acid value of 37.1 mgKOH/g solution. B C 0 011 An aqueous solution of polymer andmelamine-formaldehyde resin (the binder solution) was prepared byblending: wherein each R separately is hydrogen, methyl, or a carboxylgroup, polymer solution re ared c. 540 percent by weight of monomerunits derived from a a ab ve 154 E monovinyl aromatic compound, saidunits having the y zgi fifiw g ram 46 g structural formula: dimethylethanolamine 8.1 g H H distilled water 1331.9 g I i The solids contentof this binder solution was 10 percent by weight; thepolymer/melamine-formaldehyde resin weight ratio was 70/30. For this andand following calculations solids content or binder content is the sumof the weights of dry copolymer and melamine-formaldehyde resin.

A pigment dispersion was prepared by ball wherein R is hydrogen ormethyl,

g gxg fi gz gg 46 g d. 5-35 percent by weight of monomer units derivedfrom a binder solution 1&4 g 2-hydroxyalkyl ester of: an alpha,beta-ethylenically undistilled water 29 g saturated carboxylic acid,said units having the structural dimethyl ethanolamine 1.0 g f H R3 thenadding 30 g of binder solution and further ball milling H H during 2hours. The remainder of the binder solution was added, and thendistilled water to make the total weight of the wherein each Rseparately is hydrogen, methyl or ethyl, and each R separately ishydrogen, methyl, carboxyl or 2-hydroxyalkyl, and optionally,

e. -25 percent by weight of monomer units derived from an alkyl ester,said units having the structural formula:

monocarboxylic acid having 10 carbon atoms per molecule.

4. A copolymer as in claim 1, wherein component (b) is acrylic acid ormethacrylic acid.

5. A copolymer as in claim 1, wherein component (c) is styrene.

6. A copolymer as in claim 1, wherein component (d) is 2- hydroxy ethylmethacrylate.

7. A copolymer as in claim 1, wherein component (e) is methylmethacrylate.

8. A copolymer as in claim 1, wherein the amount of component (a) is40-70 percent by weight.

9. A copolymer as in claim 1, wherein the amount of components (b) and(c) is each 5-25 percent by weight.

10. A copolymer as in claim 1, comprising 40-60 percent by weight ofcomponent (a), 4-10 percent by weight of component (b), 10-30 percent byweight of component (c), 5-20 percent by weight of component (d), and10-25 percent by weight of component (e).

1 l. A water-thinnable binder comprising a partially neutralizedcopolymer of claim 1.

2. A copolymer as in claim 1, wherein component (a) is a vinyl esTer ofalpha-branched, saturated, aliphatic, monocarboxylic acids having from9-11 carbon atoms per molecule.
 3. A copolymer as in claim 1, whereincomponent (a) is a vinyl ester of an alpha-branched, saturated,aliphatic, monocarboxylic acid having 10 carbon atoms per molecule.
 4. Acopolymer as in claim 1, wherein component (b) is acrylic acid ormethacrylic acid.
 5. A copolymer as in claim 1, wherein component (c) isstyrene.
 6. A copolymer as in claim 1, wherein component (d) is2-hydroxy ethyl methacrylate.
 7. A copolymer as in claim 1, whereincomponent (e) is methyl methacrylate.
 8. A copolymer as in claim 1,wherein the amount of component (a) is 40-70 percent by weight.
 9. Acopolymer as in claim 1, wherein the amount of components (b) and (c) iseach 5-25 percent by weight.
 10. A copolymer as in claim 1, comprising40-60 percent by weight of component (a), 4-10 percent by weight ofcomponent (b), 10-30 percent by weight of component (c), 5-20 percent byweight of component (d), and 10-25 percent by weight of component (e).11. A water-thinnable binder comprising a partially neutralizedcopolymer of claim 1.